1. Field of the Invention
The present invention relates to telephony systems in general, and to telephony systems utilizing what is now known as intelligent networking within such systems. More particularly, it relates to telephony switching systems with enhanced switch call processing capabilities, such as those capable of supporting "call forwarding" and the like services. More particularly still, the present invention provides methods and apparatus for providing telephone number portability. In the preferred implementation of the improved method of operating a telephony switching system, novel look-ahead call routing is utilized.
2. Related Art
Today, most services are resident in the software in each central office switch. While this has allowed providers to deliver a vast array of features, it also means that providers must depend on vendors to develop new features and then must often coordinate the development of these features among the several switch vendors that they buy equipment from. When the features are available, they must then be loaded into each individual switch in the network, a complex task for networks that may contain hundreds of central offices.
As competition intensifies between providers of telephony services, providers are looking for three key competitive advantages:
They want to be able to rapidly develop customized features to differentiate their offering in the marketplace. PA1 They want to be able to quickly deploy new features ubiquitously throughout their serving areas as cost-effectively as possible. PA1 They want to put certain processing-intensive or network-based (as opposed to switch-based) services such as local number portability and PCS (Personal Communications Services) into centralized databases that all network switches can access. PA1 For the Residential Subscriber PA1 For the Business Subscriber PA1 i) transmitting from an originating switching office a called telephone number to its inherent switching office destination; PA1 ii) causing said inherent switching office to send back to said originating office a message indicating a ported telephone number; and PA1 iii) terminating connection between said originating switching office and said inherent switching office upon completion of step ii). PA1 a) transmitting from an originating switching office a called telephone number to its inherent switching office destination; PA1 b) terminating connection between said originating switching office and said inherent switching office upon not being able to establish connection to said called telephone number; PA1 c) causing said originating switching office to request a new switching office location for said called telephone number; and PA1 d) causing said originating switching office to establish connection to said new switching office.
Advanced Intelligent Networking (AIN--also know, especially outside of North America, as Intelligent Networking (IN)) is currently being deployed across the United States and Canada to provide these key advantages.
AIN places the intelligence to deliver key features in a centralized network database--called a service control point (SCP) instead of in each individual switch. "Triggers" in the software of individual service switching points (SSPs--central office switches with AIN software) momentarily interrupt call processing and generate queries of the SCP for instructions on how to process features for individual calls.
AIN also provides a standardized service creation environment (SCE) that lets any vendor, including the service provider, develop software for the SCP. Providers can then quickly create (or have other specialized companies create) custom features and load them into the SCP, where they can be immediately accessed and used by any SSP in the network.
New market entrants can either install their own AIN infrastructure, or purchase AIN capabilities from established providers.
Initial AIN features include:
Sophisticated Call Screening and Management Features that allow users to determine who can reach them and when--a call could, for instance, decide to take only long distance calls, or calls from immediate family, during dinner time, or that 900 calls could only be made during the times of the day when the parents are typically at home. PA2 Enhanced Voice Mail and Messaging Services over the public network. PA2 Personal Communications Services (PCS) that allow users to receive fully-featured calls any place in the network, wherever they happen to be. PA2 Private Virtual Networks that give users cost-effective customized networks using any combination of public and private facilities. PA2 Virtual Offices that allow users to port business features to a home or cellular telephone as they move about the network. PA2 Area Number Calling that allows a business to advertise one number throughout an area, but automatically receive calls at the branch nearest to the caller. PA2 Network and Nodal Automatic Call Distribution available from any central office. PA2 Telecopier Servers.
As may be seen from the above discussion, one of the most desirable features generally is telephone number portability; but at least local number portability (LNP), that is, number portability within a "local access and transport area" (LATA). Other desirable features involve number portability as applied to personal communications services (PCS); for example, as for cellular telephones.
It has generally been assumed that local number portability would best be provisioned through the use of some type of external database, perhaps similar to that employed for 800 service.
Regarding the point during the call at which the database is queried, it has been suggested that three basic alternatives are present. One alternative is to route the call to the terminating switch to which the NPA/NXX of the dialled number was assigned, the Terminating Access Provider (TAP)--usually the incumbent provider, performing the database query at that point, and based upon the response received back, routing the call to the actual terminating switch of the (new) Terminating Local Service Providers (TLSP). This would require that all calls to ported numbers be routed through the incumbent provider's (TAPs) facilities.
A second alternative is to have the Originating Service Provider (OSP) always perform the database query at the switch from which the call is originated, and based upon the information received back in the response, route the call direct, if possible, to the TLSP.
A third alternative is the so-called "N-1 Alternative", which states that the point at which the database query is launched (and who is responsible for launching it) is determined by the number of carriers involved in the call. If the call is local (or intra-LATA) and involves only two carriers, it is the originating carrier (i.e., OSP) that is responsible for performing the database query. If, however, the call is inter-LATA, involving an Interexchange Carrier (IC), then the intermediate carrier (i.e., IC) must perform the query to obtain final routing instructions. This assumes that the OSP can determine from the dialled NPA/NXX whether the call is local, intra-LATA or inter-LATA. Several carriers view this alternative as limiting location portability to within an NPA or LATA boundary, and as such, is better employed as an interim measure. It does, however, limit the need for OSPs to perform database queries on every originally call.
There has been discussion regarding the composition and format of the database response message which contains the routing information. It has been suggested that a new signalling parameter, Service Providers Identification (SPID) be established to merely identify which TLSP now serves the dialled number, so that the call can be routed to that provider's nearest point-of-presence (POP). It has been suggested that to gain peak network efficiency, the actual terminating switch needs to be identified.
One solution proposes that the bond between customer telephone numbers and network termination addresses be completely broken and interspersed. Under their suggestion, a number dialled to reach a ported number customer (the customer number address--CNA) would first be sent to a database for replacement with a network node address (the NNA), which would be used to route the call to the correct terminating switch. Since the NNA is in the same format at the CNA (10-digit) and its first six digits uniquely identify the terminating switch (as is the case today) NANP-based routing remains unchanged, yet customers can retain their numbers whenever they move or change providers--the CNA is simply mapped to a new NNA in the database. Since both sets of numbers use the same format, they can be interspersed, i.e., a CNA for one customer can be a NNA for another, and vice versa. It has suggested that the database populate the CNA in the Generic Address Parameter (GAP), and the NNA in the Called Party (cdPN) parameter in its response message. It was also proposed to use a new Originating Line Info (OLI) parameter value to indicate whether a database dip has already been performed in a previous node, to prevent mix-ups of CNAs with NNAs in networks where database queries may be launched at multiple points.
Another solution proposes that rather than substituting NNAs for CNAs, the database merely populates one of the assigned six-digit NPA/NXXs of the actual terminating switch in the cdPN parameter, and moves the actual dialled number to the GAP. Since all network nodes route on the first six digits of the CdPN anyway, the call will progress to the actual terminating switch, which would look at the GAP address, where the dialled number is now located, rather than the CdPN, to determine the actual called line. Although no new signalling parameters are identified with this proposal, switching software modifications, to allow a change in their treatment, are probably required.
Of significant concern with some of the portability solutions identified thus far is the need to perform database queries on all or most originating calls. The additional load on the SS7 signalling network may be such that database deployment options may be severely limited, and/or service degradations such as post dial delay, loss of transmission quality or call blocking may be experienced. One suggestion has been to limit the number of queries needed by nationally "registering" those NPA/NXXs for which numbers have become portable. This would allow carriers to launch database queries only when those prefixes are dialled. Although feasible in the near-term, many feel that once number portability begins to expand, the amount of work required in each switch to trigger on each newly-portable NPA/NXX combination will become overly burdensome. Furthermore, this methodology necessities a waiting period to ensure that all carriers have sufficient time to implement the necessary translations in each end office for each newly-portable prefix.
Absent some methodology to limit the number of queries launched to the portability database(s), the load on the SS7 signalling network may be significant. Although the existing links between the end offices and signalling hub (STP) were sufficient to handle the additional traffic, the number of new links and databases (SCPs) beyond the hub would be substantial. Therefore, if portability was widely offered, a provider's network would only be able to handle the data queries that were generated locally, not those coming in from other areas. The significance of this finding was that calls to ported numbers that originate from outside the ported number area may need to access databases separate from those handling traffic that originates within the area. This implies that unlike the LIDB (calling card database) model, multiple sets of databases, each containing data on the same numbers, may need to be deployed in different areas of the country and state.